Automated vehicle control over a highway or pathway has long been desirable. In the simplest application, the warehouse setting, such systems are relatively common. In existing systems utilized in warehouses and offices, a vehicle is usually guided over a desired path by sensing an electric current, or sensing a magnetic field. Other systems include optical sensing, radar, acoustic or video sensing systems. All of these systems are for relatively slow vehicles as they merely react to changes in direction. Each of the aforesaid systems include serious drawbacks to the development of a control system for use in a relatively high speed highway situation.
Generally stated, existing systems sense the vehicle's position relative to a desired pathway, usually the center line of the desired track, and then compensate for the vehicle being off the pathway. As a consequence, for a smooth ride the vehicle is limited to a relatively slow speed because there is no indication as to the upcoming road or path geometry. Further drawbacks particularly associated with electro magnetic systems wherein a cable is buried or located in the path, include power requirements to maintain a current in the cable. In particular power loss in the cable requires infusion of power along the pathway even in relatively short systems. Further should the cable be broken or should it become necessary to relocate the path, at least the broken section of the cable must be taken out of the pathway and the cable repositioned or relocated at some expense to the user. Finally, it has been found that insects such as termites will eat the insulation off buried cables resulting in the system shorting out. In the case of the optical systems, where a reflective path is placed in the center line of the desired track, the path may become dirty over a period of time and thus degrade operation of the system.
Existing electro-magnetic systems usually use a plurality of sensors, up to seven, mounted transversely across the vehicle to determine the track deviation. Most commonly the sensors are coil type, however, in some instances magnetometers have been used.
While radar sensing is possible along with sonar or sound sensing, one is limited in correctly reading and interpreting radar or sonar echoes to insure obstacles are avoided and turns are made properly. Video sensing techniques based on current technology, using video cameras, may operate satisfactorily in daylight and in periods of good visibility but at night and in periods of poor visibility video systems are of little or no value. Even in good visibility, video sensing systems must correctly interpret the video return. At least one echo sensing system uses a "side looking" system requiring a wall along one side of the path.
One advantage of video, radar and acoustic sensing techniques include the ability to "predict" upcoming road geometry and possibly smooth some of the vehicle corrections to maintain the desired path, however terrain recognition remains a limiting factor.
All existing systems suffer from insufficient intelligence on upcoming road geometry thus these present systems usually "react" to an off course signal when a turn occurs rather than "planning" ahead.
These different approaches may be characterized as "direct" sensing and "indirect" sensing. In direct sensing, the capabilities could include a "smart" on- board sensing system that could objectively or directly "perceive" the road geometry and the vehicle state thereby not requiring a specially designed roadway. On the other hand, an on-board sensing system that could read both vehicle state and road information indirectly from a specially designed roadway or roadside information system may be characterized as the "indirect" sensing approach.
The direct sensing approach can be analogized to video sensing which utilizes a video camera to sense the image of the upcoming road frame by frame. The data is processed and analyzed using an image processing technique. In the indirect sensing approach on the other hand, road geometry information is abstracted by several characteristic parameters and then stored in a roadway or roadside information system. Both the vehicle state and road information can be interrogated via on-board vehicle sensors or communications tools.
While the advantages of a direct sensing approach are fairly obvious, since the system essentially replicates human driving perception, it is limited by the fact that computer and image processing techniques are difficult to accomplish in "real time" using a practical size computer. On the other hand, the indirect sensing approach provides a relatively easy means of acquiring required road information as well as vehicle position relative to the center line of the desired path (lateral deviation).
In the interrogation of roadside references for stored information, only limited information need be transmitted to the vehicle, thus the amount of data to be processed is minimized. Therefore, both the on-board sensors and the roadway reference systems can be reasonably simple and economical for a large scale operation. Finally, due to the serial nature of the data, operation at relatively high speeds (80-120 km/hour) is possible. In short, it is an object of this invention to provide an indirect sensing system for vehicle control.
It is a further object of this invention to provide an indirect sensing system that provides roadway geometry or characteristics to the vehicle.
It is still another object of this invention to provide a control system in the vehicle that is responsive to both lateral deviation from a pathway obtained from the indirect sensing system and responsive to roadway characteristics which may be contained in the roadway or roadside reference systems.
It is a further object of this invention to provide an economical vehicle guidance/control system.
It is an object of this invention to provide a vehicle guidance and control system where roadway geometry information is permanently embedded in the pavement and further the roadway geometry information is safe in that it is not dependant on any outside power source.
It is still another object of this invention to provide a vehicle guidance and control system that effectively eliminates variations in signal interpretation from vertical movement caused by vehicle bounce.
It is also an object of this invention to provide a vehicle guidance and control system that based on interpreted roadway geometry provides steering signals either to a vehicle operator by way of a display or alternatively provides steering signals to the vehicle steering mechanism.
It is still another object of this invention to provide a roadway guidance/control system wherein the pathway may be readily altered.
It is another object of this invention to provide a roadway vehicle guidance/control system that utilizes passive markers.
It is still another object of this invention to provide a vehicle roadway guidance/control system wherein the passive markers may be serially oriented so that a binary code is formed by passage over the passive markers.